Effect of repetitive transcranial magnetic stimulation combined with robot-assisted training on wrist muscle activation post-stroke

OBJECTIVE: To compare the effects of active assisted wrist extension training, using a robotic exoskeleton (RW), with simultaneous 5 Hz (rTMS + RW) or Sham rTMS (Sham rTMS + RW) over the ipsilesional extensor carpi radialis motor cortical representation, on voluntary wrist muscle activation following stroke.

METHODS: The two training conditions were completed at least one week apart in 13 participants >1-year post-stroke. Voluntary wrist extensor muscle activation (motor unit (MU) recruitment thresholds and firing rate modulation in a ramp-hold handgrip task), ipsilesional corticospinal excitability (motor evoked potential [MEP] amplitude) and transcallosal inhibition were measured Pre- and Post-training.

RESULTS: For MUs active both Pre and Post training, greater reductions in recruitment thresholds were found Post rTMS + RW training (p = 0.0001) compared to Sham rTMS + RW (p = 0.16). MU firing rate modulation increased following both training conditions (p = 0.001). Ipsilesional MEPs were elicited Pre and Post in only 5/13 participants. No significant changes were seen in ipsilesional corticospinal excitability and transcallosal inhibition measures (p > 0.05).

CONCLUSIONS: Following a single rTMS + RW session in people >1-year post-stroke, changes were found in voluntary muscle activation of wrist extensor muscles. Alterations in ipsilesional corticospinal or interhemispheric excitability were not detected.

SIGNIFICANCE: The effects of rTMS + RW on muscle activation warrant further investigation as post-stroke rehabilitation strategy.